1. Field of the Invention
The present invention relates to cryogenic coolers. More specifically, the present invention relates to systems and methods for suspending and supporting cryogenic coolers.
2. Description of the Related Art
Space infrared sensor systems often require use of a cryogenic cooling subsystem to achieve increased sensor performance. Numerous types of cryogenic cooling subsystems exist, each having relatively strong and weak attributes compared to the other types. Certain space cryocoolers typically have efficiency, operational flexibility and vibration performance as strong suits. However, these strengths come at the cost of increased mass and volume relative to other available systems.
For example, the application of flexure-borne moving assemblies is one of the most important developments in modern cryocoolers because the associated high amounts of radial stiffness allow for close-tolerance non-contacting clearance seals to be used in place of traditional rubbing seals. This has resulted in a large increase in cryocooler lifetimes because the use of non-contacting clearance seals avoids the numerous contamination and degeneration issues associated with rubbing seals. The benefit of using flexure-borne moving assemblies therefore depends on the flexure system's ability to keep the moving parts properly centered in their clearance seals during operation and as external side-load forces are applied (for instance during spacecraft launch).
The mechanical realities associated with cryocooler clearance seal design dictate that some portion of the moving system's mass will be cantilevered away from the flexure system itself. Cantilevered masses are inherently more prone to sag due to externally-applied forces and measures must be taken to prevent this from happening
For example, a novel feature being proposed for the design of inline Stirling cryocoolers involves the use of a single magnetic structure to drive both the compressor and Stirling displacer pistons. In this configuration, flexure suspension systems for both the compressor and displacer pistons must be oriented in some way around the single magnetic structure.
Traditionally, the compressor suspension would be placed completely on one side of the magnetic circuit of the cryocooler, with the displacer suspension being located completely on the opposite side. Significant portions of the compressor and expander moving masses would be cantilevered away from the suspension elements. In this configuration, the individual flexure stacks in each suspension subassembly must be spaced apart in order to provide sufficient radial stiffness such that the cantilevered masses (of the compressor and expander moving elements) do not sag as side-load forces are applied. Spacing the flexures increases the effective mechanical advantage of the flexures in the radial direction.
However, this arrangement is extremely inefficient from a packaging standpoint. Specifically, the flexures on each side of the motor must be spaced a significant distance apart in order to reduce sag of the cantilevered pistons. This spacing between flexure stacks adds significant length to the overall design.
Hence, a need remains in the art for a system or method for sufficiently suspending moving elements of a system such as a cryocooler while minimizing required package volume and mass.